The long-term objective of this project is to facilitate the development of novel therapeutic targets to improve therapy for patients with AML. The two most common mutations known in patients with acute myeloid leukemia (AML) are activating mutations of the gene encoding the FLT3 receptor tyrosine kinase (RTK), and activating mutations in the Ras oncogene (NRAS and KRAS). We hypothesize that every AML tumor harbors at least one mutation in a cytokine signaling gene, and that these mutations activate downstream signaling pathways that contribute to leukemogenesis. To test these hypotheses and to identify novel drug targets, we propose the following Specific Aims: Specific Aim 1: We will comprehensively evaluate AML samples to discover the biological nature and frequency of activating mutations in receptor tyrosine kinase (RTK), non-receptor tyrosine kinase (NRTK), and Ras-MAPK pathway genes. Bone marrow and skin biopsy samples will be obtained following informed consent from patients at our institution with de novo or relapsed AML. In collaboration with the Washington University Genome Sequencing Center (GSC), we will screen for mutations by total exonic resequencing of all known RTK, NRTK and Ras-MAPK pathway genes in patients with AML. Novel mutations identified by the GSC will be characterized using biochemical, cell culture and mouse model assays. Specific Aim 2: We will test potential cooperative functional interactions between mutations in cytokine signaling pathway genes with transcription factor mutations in mice. A mouse model of AML has been developed by coexpressing the RTK fusion oncogene TEL-PDGFRB with the AML1-ETO transcription factor oncogene, providing proof of principle that cytokine signaling pathway mutations provide a critical function in the development of leukemia. Signaling mutants of TEL-PDGFRB and gain-of-function mutations of the AKT/PKB, NRas and STAT5a genes will be coexpressed with AML1-ETO or PML-RARA in primary murine hematopoietic cells to identify signaling pathways that cooperate to cause acute leukemia in mice. Lastly, novel mutations in cytokine signaling genes identified in Aim 1 will also be tested for their ability to induce leukemia via cooperation with transcription factor fusion oncogenes in vivo.